The present invention relates to a process for preparing a reaction layer of a gas permeable electrode employed, for example, in a fuel cell, a secondary battery, an electrochemical reactor, an anode for plating or the like.
Heretofore, such gas permeable electrodes have been prepared by mixing carbon powder supporting a platinum catalyst and polytetrafluoroethylene (hereinafter referred to as "PTFE"), pressing the resultant mixture and then sintering it to provide the reaction layer of the gas permeable electrode.
Unfortunately, in a gas permeable electrode so prepared the carbon powder and the PTFE powder may not be desirably sintered as intended by pressing, so that the reaction layer is relaxed by means of high temperature thermal expansion of the powders resulting in electrolyte passages and gas passages that are disconnected. As a result, portions of the platinum catalyst in the reaction layer cannot contact the electrolyte to take part in the reaction. This insufficient contact area between the electrolyte and the gas results in a lowering of the catalyst performance.